Titanium-doped high-nickel ternary positive electrode material and preparation method thereof

Abstract

The application provides a titanium-doped high-nickel ternary positive electrode material and a preparation method thereof. The titanium-doped high-nickel ternary positive electrode material comprises a high-nickel ternary positive electrode material and a titanium-doped element; the content of the titanium-doped element accounts for 0.5-5wt% of the titanium-doped high-nickel ternary positive electrode material. The preparation steps comprise the following steps: preparing a nickel-cobalt-manganese hydroxide precursor; mixing the nickel-cobalt-manganese hydroxide precursor with a lithium source uniformly and then sintering and cooling to obtain a high-nickel ternary positive electrode material; mixing the high-nickel ternary positive electrode material with a reducing titanium source and sintering to obtain the titanium-doped high-nickel ternary positive electrode material. The reducing titanium is used to modify the high-nickel ternary material, the more stable Ni 2+ is enriched on the surface of the material as a protective layer, the corrosion of the electrolyte to the material is reduced, and the surface stability of the material is improved; the titanium element is more easily introduced into the material crystal lattice than general doping methods; the material crystal lattice structure strength is improved through the strong Ti-O bond, and excellent cycle stability and rate performance are obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium battery positive electrode materials, and particularly relates to a titanium-doped high-nickel ternary positive electrode material and a preparation method thereof. BACKGROUND

[0002] The high-nickel ternary positive electrode material Li(Ni x Co y Mn 1-x-y )O2 (LNCM) has higher specific capacity and energy density, has greater advantages in the application of new lithium-ion batteries, and is considered to be one of the most promising power lithium-ion battery positive electrode materials. However, the high-nickel positive electrode material has problems such as easy phase change of surface particles, poor rate and cycle performance, unstable surface structure, poor thermal stability and the like. The stability of the high-nickel ternary material can be improved to some extent and the electrochemical performance of the material can be improved through structural modification.

[0003] A patent document with the publication number CN112736229 A discloses a reduction-modified lithium positive electrode material and a preparation method thereof. The method is to use hypophosphorous acid and / or hypophosphite as a reducing agent, to pre-treat the reducing agent to make the reducing agent as uniformly as possible coated on the surface of the lithium positive electrode material, to construct an interface phase structure of spinel phase and / or rock salt phase on the surface, so as to protect the material body from being eroded by the electrolyte and to improve the cycle stability of the material. The method selects calcium hypophosphite, sodium hypophosphite, hypophosphorous acid and magnesium hypophosphite as the reducing agent to modify the positive electrode material, and uses the reducing gas PH3 generated by high-temperature decomposition to modify the surface of the material. The method makes the coating layer more compact through reaction to achieve uniform and firm coating, but does not explain the specific reaction of modification and how to achieve tight coating. Moreover, the method involves using water as a solvent in the experimental process, and water will seriously affect the performance of the high-nickel positive electrode material. Moisture on the surface layer of the material will generate inert lithium salt, destroy the material structure and reduce the material performance. The humidity needs to be controlled during the coating process of the high-nickel material, and the process is generally carried out in a water-free environment. In addition, the use of gas to modify the material is affected by many factors such as gas flow rate, concentration, temperature and time, and the amount of reducing agent is difficult to accurately control, which has no obvious guiding significance for the use of reducing agent to modify the positive electrode material, and is not conducive to industrial application. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the deficiencies and defects mentioned in the above background, and to provide a titanium-doped high-nickel ternary positive electrode material with good structural stability, cycle performance, rate performance and other electrochemical properties, and a preparation method thereof.

[0005] To solve the above technical problems, the technical solution provided by the present application is as follows:

[0006] The application discloses a titanium-doped high-nickel ternary positive electrode material, and relates to the technical field of lithium ion batteries.

[0007] The application utilizes the titanium with reducibility to modify the high-nickel ternary material, and makes the more stable Ni 2+ The titanium element is easier to enter the material lattice than general doping methods, the material lattice structure strength is improved through the strong Ti-O bond, and excellent cycle stability and rate performance are obtained.

[0008] Further preferably, the high-nickel ternary positive electrode material has a chemical formula of LiNi x Co y Mn (1-x-y) O2, wherein 0.75 < x < 0.95 and 0.025 < y < 0.1.

[0009] The bulk density of the powder material is closely related to the morphology, particle size and distribution of the powder material. Irregular powder particles have serious agglomeration and ion bridging phenomena when mixed, and there are large gaps between particles when the particles are packed, so the powder has low bulk density. When regular spherical particles are packed, the contact surface between particles is small, there is no agglomeration and particle bridging, there are fewer gaps between particles, and the powder has high bulk density. The morphology, particle size and other microstructures of the positive electrode material depend on the precursor, and the sphericalization of the precursor material particles is an effective way to improve the bulk density and volume specific capacity of the material, and the spherical product has excellent flowability, dispersibility and processability. Therefore, the sphericalization can improve the compaction density and volume specific capacity of the positive electrode material and improve the processability and quality of the electrode sheet. The titanium-doped high-nickel ternary positive electrode material obtained by mixing the compound with reducible titanium with the high-nickel ternary positive electrode material and then solid-phase sintering is in a spherical shape, so that the morphology and particle size distribution of the secondary spherical particles of the original ternary material are ensured.

[0010] Based on the same technical idea, the application further provides a preparation method of the titanium-doped high-nickel ternary positive electrode material.

[0011] (1) preparing a nickel-cobalt-manganese hydroxide precursor by a coprecipitation reaction;

[0012] (2) After the nickel-cobalt-manganese hydroxide precursor obtained in step (1) is mixed evenly with the lithium source, it is sintered in two stages under an oxidizing atmosphere and cooled to room temperature to obtain a high-nickel ternary cathode material.

[0013] (3) Thoroughly mix the high-nickel ternary cathode material obtained in step (2) with the reducing titanium source;

[0014] (4) The mixed powder obtained in step (3) is sintered at high temperature under an inert atmosphere, and cooled after a period of time to obtain titanium-doped high-nickel ternary cathode material.

[0015] High-nickel materials suffer from surface instability, transition metal dissolution, and electrolyte corrosion, especially those with highly reactive Ni surfaces. 3+ In large quantities, the reaction with the electrolyte can lead to surface structure deterioration, lattice oxygen evolution, and the formation of electrochemically inert substances. Modifying the cathode material with a metal reducing agent, through a redox reaction, allows Ni to... 3+ Reduced to stable Ni 2+ and make Ti 4+ Better incorporation into the material lattice can stabilize the material structure and improve rate and cycling performance. At the same time, stronger Ti-O bonds can enhance the structural strength of the material and suppress the precipitation of lattice oxygen caused by charge transfer, thereby improving the cycling stability and rate performance of the material.

[0016] More preferably, the preparation of nickel cobalt manganese hydroxide precursor by co-precipitation reaction in step (1) above refers to pumping a mixed solution of nickel cobalt manganese into a continuously stirred reactor containing an aqueous ammonia solution, heating it and passing it through a protective atmosphere, while simultaneously pumping in a complexing agent and a precipitant solution, stirring to carry out a co-precipitation reaction, aging, filtering, washing, and drying to obtain the nickel cobalt manganese hydroxide precursor.

[0017] More preferably, the nickel source, manganese source, and cobalt source in the above-mentioned nickel-cobalt-manganese mixed solution are soluble nickel salt, soluble manganese salt, and soluble cobalt salt, respectively; the total molar concentration of nickel, cobalt, and manganese ions in the nickel-cobalt-manganese mixed solution is 0.1-3.0 mol / L, and the molar ratio of nickel, cobalt, and manganese ions is (7.5-9.5):(0.25-2.5):(0.25-2.5); the feeding rate of the nickel-cobalt-manganese mixed solution is 80-120 mL / h.

[0018] If the concentration of metal ions in the nickel-cobalt-manganese mixed solution is too low, it will hinder the subsequent precipitation process and result in a longer precipitation time, which is detrimental to improving production efficiency. If the concentration of metal ions is too high, it will hinder the complete dissolution of the metal salt. If the feeding rate is too fast, it will lead to a large pH range, making it difficult for the precipitant to effectively precipitate the metal ions, which is not conducive to controlling the formation and growth of crystal nuclei in the reaction process. If the feeding rate is too slow, the particles are prone to agglomeration, which is also detrimental to improving production efficiency.

[0019] Further preferably, the soluble nickel salt is one or more of nickel sulfate, nickel nitrate, nickel acetate, or nickel chloride, and hydrates thereof; the soluble cobalt salt is one or more of cobalt sulfate, cobalt nitrate, cobalt acetate, or cobalt chloride, and hydrates thereof; and the soluble manganese salt is one or more of manganese sulfate, manganese nitrate, manganese acetate, or manganese chloride, and hydrates thereof. The total molar concentration of nickel, cobalt, and manganese ions in the nickel-cobalt-manganese mixed solution is more preferably 1.5-2.5 mol / L. The feeding speed of the nickel-cobalt-manganese mixed solution is more preferably 90-110 mL / h.

[0020] Further preferably, the complexing agent is an aqueous ammonia solution having a mass concentration of 25-28%; the ammonia concentration of the reaction system is adjusted to 0.1-5.0 mol / L using the aqueous ammonia solution; the precipitant is one or more of sodium hydroxide, potassium hydroxide, or lithium hydroxide, and the molar concentration of the precipitant solution is 1.0-7.0 mol / L; the pH value of the reaction system is adjusted to 10-12 using the precipitant solution; and the volume ratio of the aqueous ammonia solution, the precipitant solution, and the nickel-cobalt-manganese mixed solution is (0.1-10):(1-2):(1-2).

[0021] If the molar concentration of the aqueous ammonia solution is too low, the metal ions are difficult to be completely complexed, and if the molar concentration of the aqueous ammonia solution is too high, it is not conducive to the formation of hydroxide precipitates of the metal ions. If the molar concentration of the hydroxide precipitant solution is too high or too low, the reaction process cannot be accurately controlled. At the above-mentioned pH value, it is more conducive to controlling the growth rate of the particles to be neither too fast nor too slow. At the above-mentioned volume feeding ratio of the aqueous ammonia solution, the precipitant solution, and the nickel-cobalt-manganese mixed solution, it is conducive to the formation of crystal grains and the growth of crystals in the crystallization process.

[0022] Further preferably, the stirring speed during the co-precipitation reaction is controlled to be 800-1200 r / min, the temperature is 30-60°C, and the time is 30-50 h; the aging temperature is 30-60°C; the washing is cross washing the filter cake with deionized water and ethanol for ≥6 times in sequence; and the drying temperature is 80-100°C, and the time is 12-24 h.

[0023] If the stirring speed is too slow, the primary particles are prone to agglomeration, and if the stirring speed is too fast, the growing crystals are prone to breakage; in the above temperature range, the crystal growth is more favorable; the reaction time is determined by the raw material content and the feeding speed. The aging process can replace the sulfate anions inside the material and is conducive to the uniformity of the particle surface. If the aging time is too short, it is difficult to ensure ion exchange of the anions, which also affects the subsequent washing process, and if the aging time is too long, it is not conducive to production application and the uniformity of the material surface. The aging temperature is consistent with the co-precipitation reaction temperature, which is conducive to the uniform dispersion of the material and prevents agglomeration, and ensures the uniform growth of the primary particles into secondary particles. If the drying temperature is too low or the time is too short, the material is difficult to dry, and if the temperature is too high or the time is too long, the material surface will have other side reactions, affecting the material performance, and the long period is not conducive to industrial production.

[0024] Further preferably, the temperature during stirring in the co-precipitation reaction is more preferably 40-50°C. The temperature of the aging is more preferably 40-50°C.

[0025] Further preferably, in the step (2), the lithium source is lithium hydroxide and / or lithium carbonate, and the molar ratio of the total moles of nickel, cobalt and manganese elements in the nickel-cobalt-manganese hydroxide precursor to the moles of lithium element in the lithium source is 1:(1.02-1.2).

[0026] Further preferably, in the step (2), the two-stage sintering is first heated to 350-550°C at a heating rate of 1-10°C / min, sintered for 2-8h, and then heated to 550-1000°C at a heating rate of 1-10°C / min, sintered for 8-20h.

[0027] Further preferably, the two-stage sintering is first heated to 400-500°C at a heating rate of 3-7°C / min, sintered for 3-6h, and then heated to 600-900°C at a heating rate of 3-7°C / min, sintered for 10-16h.

[0028] In the two-stage heating sintering process, the temperature of the second stage sintering is higher than that of the first stage sintering. In the first stage sintering process, the decomposition reaction of the precursor and the lithium source mainly occurs, and in the second stage sintering process, the compound reaction of the oxides decomposed from the precursor and the lithium source in the oxygen atmosphere mainly occurs. If the sintering temperature is too high or the time is too long, the material is prone to agglomeration or even clumping, and the capacity is difficult to release in the charging and discharging process, and if the calcination temperature is too low or the time is too short, it is difficult to form the desired morphology, affecting the electrochemical performance. If the heating rate is too fast, it is difficult to ensure that the material is fully reacted, especially affecting the diffusion of lithium ions to the interior of the material structure, and if the heating rate is too slow, it is not conducive to industrial production.

[0029] Further preferably, in the step (3), the mass ratio of the high-nickel ternary positive electrode material to the reducing titanium source is 1:(0.005-0.05); and the titanium source is one or more of titanium monoxide, titanium dichloride, titanium dibromide and other compounds containing reducing titanium.

[0030] Further preferably, in the step (3), the mass ratio of the high-nickel ternary positive electrode material to the titanium monoxide is 1:(0.005-0.05). If the amount of the titanium source is too large, the unreacted titanium-containing substances on the surface of the material will accumulate too much, which will affect the reaction process kinetics of the material and thus affect the performance of the material. If the amount of the titanium source is too small, the modification effect cannot be achieved, and the raw materials are wasted.

[0031] Further preferably, in the step (4), the high-temperature sintering is performed at a temperature increasing rate of 1-10 ℃ / min to 300-500 ℃ for 3-5 h; and the inert atmosphere is an argon atmosphere and / or a nitrogen atmosphere.

[0032] Further preferably, the high-temperature sintering is performed at a temperature increasing rate of 3-7 ℃ / min to 400 ℃ for 3-5 h.

[0033] The purpose of the sintering treatment is mainly to allow the titanium source to be adsorbed on the surface of the high-nickel ternary material, and to make Ti 2+ react with Ni 3+ so that Ti 4+ enters the crystal lattice of the material better to form a stable Ni 2+ layer. If the temperature increasing rate is too fast, the reaction of the material cannot be ensured to be sufficient, and if the temperature increasing rate is too slow, the industrial production is not conducive. If the sintering temperature is too low, Ti 2+ cannot be oxidized to form Ti 4+ , and if the sintering temperature is too high, the ions may enter the material body phase too fast, causing uneven modification. If the sintering time is too short, the reaction is not complete, and if the sintering time is too long, unnecessary side reactions occur, and the production efficiency is affected.

[0034] Compared with the prior art, the present application has the following beneficial effects:

[0035] (1) The present application uses reducing titanium to modify the high-nickel ternary material, and through the oxidation-reduction reaction, more stable Ni 2+ is enriched on the surface of the material as a protective layer to reduce the corrosion of the electrolyte on the material and improve the surface stability of the material; at the same time, the titanium element is more easily entered into the crystal lattice of the material than in the general doping method; the material lattice structure strength is improved through the strong Ti-O bond to obtain excellent cycle stability and rate performance.

[0036] (2) The titanium-doped high-nickel ternary positive electrode material prepared by the method has a spherical secondary particle agglomerate, an average particle size of 3 microns, a regular morphology and a uniform distribution, and excellent cycle stability and rate performance.

[0037] (3) The method for preparing the high-nickel ternary positive electrode material by the solid-phase sintering method is simple in process, low in reaction temperature, low in raw material cost and suitable for industrialized production. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0039] Figure 1 is an XRD graph of the titanium-doped high-nickel ternary positive electrode material of the embodiment 1 of the present application;

[0040] Figure 2 is an SEM graph of the titanium-doped high-nickel ternary positive electrode material of the embodiment 1 of the present application;

[0041] Figure 3 is an EDS Mapping graph of the titanium-doped high-nickel ternary positive electrode material of the embodiment 1 of the present application;

[0042] Figure 4 is a charge-discharge cycle curve and charge-discharge coulomb curve graph of the battery assembled by the titanium-doped high-nickel ternary positive electrode material of the embodiment 1 of the present application;

[0043] Figure 5 is a different rate discharge curve graph of the battery assembled by the titanium-doped high-nickel ternary positive electrode material of the embodiment 1 of the present application. DETAILED DESCRIPTION

[0044] In order to facilitate the understanding of the present application, the present application will be described more fully and specifically below in conjunction with the drawings of the specification and the preferred embodiments, but the protection scope of the present application is not limited to the following specific embodiments.

[0045] Unless otherwise defined, all the professional terms used in the following are the same as the meanings commonly understood by those skilled in the art. The professional terms used in the present application are only for the purpose of describing the specific embodiments and are not intended to limit the protection scope of the present application.

[0046] Unless otherwise specifically indicated, all materials, reagents, and equipment used in the present application are commercially available or are prepared by known methods.

[0047] The present application utilizes the surface of titanium-doped high-nickel ternary positive electrode material with reducing property to obtain stable Ni 2+ and Ti 4+ doped surface, improve the cycle performance and rate performance of the material. Specifically, uniformly mix under inert atmosphere and high-temperature heat treatment, reduce the high-reactivity Ni 3+ on the surface of the material to stable Ni 2+ through oxidation-reduction reaction, oxidize Ti 2+ to Ti 4+ , and then better incorporate titanium into the lattice, and the stable surface Ni 2+ layer inhibits the side reaction on the material surface during the charge and discharge cycle process, prevents the corrosion of electrolyte, and the generated Ni 2+ suppresses the oxidation of lattice oxygen due to charge balance, alleviates the precipitation of lattice oxygen caused by spontaneous reduction of Ni 3+ on the surface, reduces the formation of oxygen vacancies, enhances the structural stability of the material, and improves the cycle performance. The Ti-O bond has strong dissociation energy, enters the lattice to improve the structural strength, inhibits the structure collapse in the delithiation state, provides more lithium ion transmission channels, reduces the generation of micro-cracks, and to some extent enhances the rate performance of the material. The following will be further illustrated in combination with examples.

[0048] Example 1

[0049] A titanium-doped high-nickel ternary positive electrode material and a preparation method thereof.

[0050] The positive electrode material is made of titanium-doped high-nickel ternary positive electrode material LiNi 0.9 Co 0.05 Mn 0.05 O2, the content of titanium monoxide in the titanium-doped high-nickel ternary positive electrode material accounts for 1% of the positive electrode material, LiNi 0.9 Co 0.05 Mn 0.05 O2 is a spherical secondary particle agglomerate with an average particle size of 3 μm, regular morphology, and uniform distribution.

[0051] The preparation method of the titanium-doped high-nickel ternary positive electrode material in the present embodiment includes the following steps:

[0052] (1) A 4L mixed solution of transition metals, nickel sulfate, cobalt sulfate and manganese sulfate, wherein the total molar concentration of Ni, Co and Mn ions is 2.0 mol / L, is pumped into a reactor containing 2L of 2 mol / L ammonia solution at a feeding rate of 100 mL / h. At the same time, the ammonia concentration of the reaction system is adjusted to 2 mol / L with 25% ammonia solution. The pH of the reaction system is adjusted to 11.4 with 4L of 5 mol / L sodium hydroxide precipitant solution. The reaction system is heated and stirred at 1000 r / min and 50℃ for 20 h for co-precipitation. After that, it is stirred and aged at 45℃ for 12 h. After filtration, the filter is washed 6 times with deionized water and ethanol respectively. After drying at 90℃ for 12 h, nickel cobalt manganese hydroxide precursor is obtained.

[0053] (2) 2.0 g of the nickel-cobalt-manganese hydroxide precursor (Ni 30.6696 mmol, Co 1.6968 mmol, Mn 1.8201 mmol) obtained in step (1) was mixed with 0.9478 g (35.8958 mmol) of lithium hydroxide monohydrate and ball-milled. Under a high-purity oxygen atmosphere, the temperature was first increased to 450 °C at a rate of 5 °C / min and sintered for 4 h. Then, the temperature was increased to 700 °C at a rate of 5 °C / min and sintered for 12 h. This two-stage sintering was carried out. After cooling to room temperature, high-nickel ternary LiNi was obtained. 0.9 Co 0.05 Mn 0.05 O2 cathode material;

[0054] (3) Mix 0.01 g of titanium monoxide powder obtained in step (2) with 1.0 g of high-nickel ternary LiNi 0.9 Co 0.05 Mn 0.05 The O2 cathode material was thoroughly and uniformly mixed during ball milling.

[0055] (4) The powder obtained in step (3) is transferred into a tube furnace and heated to 400°C at a rate of 5°C / min under an argon atmosphere. It is sintered for 4 h and then cooled to room temperature to obtain titanium-doped high-nickel ternary cathode material.

[0056] like Figure 1 As shown, the titanium-doped high-nickel ternary cathode material of this embodiment has characteristic peaks that match those of the PDF card LiNiO2 (PDF#85-1966) (because the high-nickel ternary cathode material has a very high nickel content, the characteristic peaks reflected by XRD are almost the same as those of pure lithium nickelate, and the structural characteristics are consistent), and no impurity phases are generated.

[0057] like Figure 2 As shown, the titanium-doped high-nickel ternary cathode material in this embodiment has a good morphology, inheriting the morphology of the high-nickel ternary cathode material. The secondary particles are spherical with an average particle size of 3 μm.

[0058] As shown in Figure 3 EDS mapping results of the titanium-doped high-nickel ternary positive electrode material of the present embodiment show that the titanium element is uniformly distributed in the material.

[0059] Battery assembly: 0.08 g of the titanium-doped high-nickel ternary positive electrode material obtained in the present embodiment was weighed, 0.01 g of acetylene black was added as a conductive agent, and 0.01 g of PVDF polyvinylidene fluoride was added as a binder, and N-methyl pyrrolidone was used as a solvent to mix and grind to form a positive electrode material; the obtained positive electrode material was coated on the surface of an aluminum foil to form a pole piece; in an argon-filled airtight glove box, the pole piece was used as the positive electrode, a lithium metal piece was used as the negative electrode, a microporous polypropylene film was used as the separator, 1 mol / L LiPF6 / EC:DMC:EMC (volume ratio 1:1:1) was used as the electrolyte, a CR2025 button cell was assembled, and charge-discharge performance test was carried out.

[0060] As shown in Figure 4 The battery assembled by the method of the titanium-doped high-nickel ternary positive electrode material obtained in the present embodiment has a first discharge specific capacity of 211.1 mAh / g, a charge specific capacity of 232.7 mAh / g, a first charge-discharge coulombic efficiency of 90.71%, and a discharge specific capacity of 197.1 mAh / g after 100 cycles, with a capacity retention rate of 93.37%, under a charge-discharge voltage of 2.7-4.5 V and a current density of 1 C (200 mA / g). Under a current density of 5 C (1000 mA / g), the first discharge specific capacity is 182.2 mAh / g, the charge specific capacity is 211.6 mAh / g, the first charge-discharge coulombic efficiency is 86.11%, and the discharge specific capacity is still as high as 156.1 mAh / g after 150 cycles, with a capacity retention rate of 85.68%. This indicates that the method of the titanium-doped high-nickel ternary positive electrode material is beneficial to the transmission of lithium ions during high-voltage and high-rate charge-discharge cycling, and the discharge specific capacity, charge-discharge performance and coulombic efficiency are stable, and the cycling performance is good.

[0061] As shown in Figure 5 The rate curve of the battery assembled by the method of the titanium-doped high-nickel ternary positive electrode material obtained in the present embodiment shows that the discharge specific capacity can reach 174.4 mAh / g under a current density of 10 C (2000 mA / g) and a charge-discharge voltage of 2.7-4.5 V, and the discharge specific capacity can still be as high as 142.2 mAh / g after 150 cycles, with a capacity retention rate of 81.53%, further indicating that the high-nickel ternary material is modified by titanium monoxide, and the lithium ion transmission performance during charge-discharge cycling is improved, and excellent electrochemical performance can still be provided under high voltage.

[0062] Example 2

[0063] The positive electrode material is titanium-doped high-nickel ternary positive electrode material LiNi 0.9 Co 0.05 Mn 0.05 O2, the content of titanium monoxide in the titanium-doped high-nickel ternary positive electrode material accounts for 0.5% of the positive electrode material, LiNi 0.9 Co 0.05 Mn 0.05 O2 is a spherical secondary particle agglomerate, the average particle size is 3 μm, the morphology is regular, and the distribution is uniform.

[0064] The preparation method of the titanium-doped high-nickel ternary positive electrode material in the embodiment comprises the following steps:

[0065] (1) The same as step (1) of Example 1;

[0066] (2) The same as step (2) of Example 1;

[0067] (3) 0.005 g of titanium monoxide powder obtained in step (2) is mixed with 1.0 g of high-nickel ternary LiNi 0.9 Co 0.05 Mn 0.05 O2 positive electrode material in a ball mill to make them uniformly mixed;

[0068] (4) The powder obtained in step (3) is transferred into a tube furnace, and heated to 400℃ at a rate of 5 ℃ / min under an argon atmosphere, sintered for 4 h, and cooled to room temperature to obtain the titanium-doped high-nickel ternary positive electrode material.

[0069] Battery assembly: the same as Example 1;

[0070] The battery assembled by the titanium-doped high-nickel ternary positive electrode material obtained in the embodiment has a first discharge specific capacity of 179.2 mAh / g, a charge specific capacity of 220.6 mAh / g, a first charge-discharge coulombic efficiency of 81.22%, and a discharge specific capacity of 135.5 mAh / g after 150 cycles, and the capacity retention rate is 75.61% under a charge-discharge voltage of 2.7-4.5 V and a current density of 5 C (1000 mA / g). Compared with the detection results of Example 1, it is shown that the method of the titanium-doped high-nickel ternary positive electrode material in the embodiment is beneficial to the transmission of lithium ions in the charge-discharge process, the discharge specific capacity, the charge-discharge performance and the coulombic efficiency are stable, and the cycle performance is good, but the amount of titanium monoxide is less, the surface structure modification of the material is not complete, and the cycle stability is less improved.

[0071] Example 3

[0072] The positive electrode material is titanium-doped high-nickel ternary positive electrode material LiNi 0.9 Co 0.05 Mn 0.05O2, the content of titanium monoxide in the titanium-doped high-nickel ternary positive electrode material accounts for 1.5% of the positive electrode material, LiNi 0.9 Co 0.05 Mn 0.05 O2 is a spherical-like secondary particle agglomerate with an average particle size of 3 μm, regular morphology and uniform distribution.

[0073] The preparation method of the titanium-doped high-nickel ternary positive electrode material in the embodiment includes the following steps:

[0074] (1) The same as step (1) of Example 1;

[0075] (2) The same as step (2) of Example 1;

[0076] (3) 0.015 g of titanium monoxide powder obtained in step (2) is fully mixed with 1.0 g of high-nickel ternary LiNi 0.9 Co 0.05 Mn 0.05 O2 positive electrode material in the ball mill;

[0077] (4) The powder obtained in step (3) is transferred into a tube furnace, and is heated to 400 ℃ at a rate of 5 ℃ / min under an oxygen atmosphere, sintered for 4 h, and cooled to room temperature to obtain the titanium-doped high-nickel ternary positive electrode material.

[0078] Battery assembly: the same as Example 1.

[0079] The battery assembled by the titanium-doped high-nickel ternary positive electrode material obtained in the embodiment has a first discharge specific capacity of 170.2 mAh / g, a charge specific capacity of 214.2 mAh / g, a first charge-discharge coulombic efficiency of 89.34%, and a discharge specific capacity of 124.5 mAh / g after 150 cycles, and the capacity retention rate is 73.15% under a charge-discharge voltage of 2.7-4.5 V and a current density of 5 C (1000 mA / g). Compared with the detection results of Example 1, it is shown that the method of the titanium-doped high-nickel ternary positive electrode material in the embodiment is beneficial to the transmission of lithium ions in the charge-discharge process, the discharge specific capacity, the charge-discharge performance and the coulombic efficiency are stable, and the cycle performance is good, but too much titanium monoxide will cause too much electrochemically inert substance, resulting in capacity loss.

[0080] Example 4

[0081] The titanium-doped high-nickel ternary positive electrode material of the embodiment is the same as that of Example 1.

[0082] The preparation method of the titanium-doped high-nickel ternary positive electrode material in the embodiment includes the following steps:

[0083] (1) The same as step (1) of Example 1;

[0084] (2) The same as step (2) of Example 1;

[0085] (3) The 0.01 g titanium monoxide powder obtained in step (2) is mixed with 1.0 g high-nickel ternary LiNi 0.9 Co 0.05 Mn 0.05 O2 positive electrode material in a ball mill to obtain a mixture;

[0086] (4) The powder obtained in step (3) is transferred into a tube furnace and heated to 500 ℃ at a rate of 5 ℃ / min under an oxygen atmosphere, and sintered for 4 h, and then cooled to room temperature to obtain the titanium-doped high-nickel ternary positive electrode material.

[0087] Battery assembly: the same as Example 1.

[0088] The battery assembled from the titanium-doped high-nickel ternary positive electrode material obtained in this example has a first discharge specific capacity of 171.4 mAh / g, a charge specific capacity of 210.6 mAh / g, a first charge-discharge coulombic efficiency of 82.33%, and a discharge specific capacity of 126.1 mAh / g after 150 cycles, and a capacity retention rate of 73.57% under a charge-discharge voltage of 2.7-4.5 V and a current density of 5 C (1000 mA / g). Compared with the detection results of Example 1, it is shown that the method of titanium-doped high-nickel ternary positive electrode material in this example is beneficial to the transmission of lithium ions during the charge-discharge process, and the discharge specific capacity, charge-discharge performance and coulombic efficiency are stable, and the cycle performance is good, but the modification temperature is too high, which causes the titanium monoxide to react too quickly on the surface of the material, resulting in accumulation and forming an uneven surface structure, which reduces the high-rate lithium ion transmission efficiency and the capacity and cycle stability.

[0089] Example 5

[0090] The titanium-doped high-nickel ternary positive electrode material of this example is the same as that of Example 1.

[0091] The above method for preparing a titanium-doped high-nickel ternary positive electrode material comprises the following steps:

[0092] (1) The same as step (1) of Example 1;

[0093] (2) The same as step (2) of Example 1;

[0094] (3) The 0.01 g titanium monoxide powder obtained in step (2) is mixed with 1.0 g high-nickel ternary LiNi 0.9 Co 0.05 Mn 0.05 O2 positive electrode material in a ball mill to obtain a mixture;

[0095] (4) The powder obtained in step (3) is transferred into a tube furnace and heated to 300℃ at a rate of 5 ℃ / min under an oxygen atmosphere, sintered for 4 h, and cooled to room temperature to obtain a titanium monoxide modified high-nickel ternary positive electrode material.

[0096] Battery assembly: same as Example 1.

[0097] The battery assembled from the titanium doped high-nickel ternary positive electrode material obtained in this example has a first discharge specific capacity of 172.8 mAh / g, a charge specific capacity of 215.6 mAh / g, a first charge-discharge coulombic efficiency of 80.13%, and a discharge specific capacity of 133.9 mAh / g after 150 cycles, with a capacity retention rate of 77.48%, at a charge-discharge voltage of 2.7-4.5 V and a current density of 5 C (1000 mA / g). Compared with the detection results of Example 1, the method of titanium doped high-nickel ternary positive electrode material in this example is beneficial to the transmission of lithium ions during the charge-discharge process, and has stable discharge specific capacity, charge-discharge performance and coulombic efficiency, and good cycle performance. However, the modification temperature is too low, which may cause insufficient reaction and cause irreversible capacity loss.

[0098] Comparative Example 1

[0099] The positive electrode material is a high-nickel ternary positive electrode material LiNi 0.9 Co 0.05 Mn 0.05 O2, and LiNi 0.9 Co 0.05 Mn 0.05 O2 is a spherical secondary particle agglomerate with an average particle size of 3 μm, regular morphology and uniform distribution.

[0100] The preparation method of the high-nickel ternary positive electrode material of this comparative example comprises the following steps:

[0101] (1) Same as step (1) of Example 1.

[0102] (2) Same as step (2) of Example 1.

[0103] Battery assembly: same as Example 1.

[0104] The battery assembled by the unmodified high-nickel ternary positive electrode material obtained in the present comparative example has a first discharge specific capacity of 210.3 mAh / g, a charge specific capacity of 248.8 mAh / g, a first charge-discharge coulombic efficiency of 84.52%, a discharge specific capacity of 179.5 mAh / g after 80 cycles, and a capacity retention rate of 85.36% under a charge-discharge voltage of 2.7-4.5 V and a current density of 1C (200 mA / g). Under a current density of 5C (1000 mA / g), the discharge specific capacity is 177.2 mAh / g, and the discharge specific capacity is only 121.5 mAh / g after 150 cycles, with a capacity retention rate of 68.57%. Under a current density of 10C (2000 mA / g), the discharge specific capacity is 165.8 mAh / g. Compared with the test results of Example 1, the results of the present comparative example show that the unmodified material has a large irreversible capacity loss in charge-discharge reaction, poor cycle stability and poor rate performance.

[0105] Comparative Example 2

[0106] A titanium-doped high-nickel ternary positive electrode material and a preparation method thereof.

[0107] The positive electrode material is made of a titanium-doped high-nickel ternary positive electrode material LiNi 0.9 Co 0.05 Mn 0.05 O2, and the content of titanium dioxide in the titanium-doped high-nickel ternary positive electrode material accounts for 1% of the positive electrode material. LiNi 0.9 Co 0.05 Mn 0.05 O2 is a spherical secondary particle agglomerate with an average particle size of 3 μm, regular morphology and uniform distribution.

[0108] The preparation method of the titanium-doped high-nickel ternary positive electrode material of the present comparative example comprises the following steps:

[0109] (1) The same as step (1) of Example 1;

[0110] (2) The same as step (2) of Example 1;

[0111] (3) 0.01 g of titanium dioxide powder obtained in step (2) and 1.0 g of high-nickel ternary LiNi 0.9 Co 0.05 Mn 0.05 O2 positive electrode material are fully mixed and uniformly distributed in a ball mill;

[0112] (4) The powder obtained in step (3) is transferred into a tube furnace, heated to 400℃ at a rate of 5 ℃ / min under an argon atmosphere, sintered for 4 h, and cooled to room temperature to obtain the titanium-doped high-nickel ternary positive electrode material.

[0113] Battery assembly: the same as Example 1;

[0114] The battery assembled from the titanium dioxide modified high-nickel ternary positive electrode material of the present comparative example has a first discharge specific capacity of 201.7 mAh / g at a charge-discharge voltage of 2.7-4.5 V and a current density of 1C (200 mA / g), and a discharge specific capacity of 183.1 mAh / g after 100 cycles, with a capacity retention rate of 90.77%. Compared with the titanium monoxide doped modified high-nickel material, the discharge specific capacity is lower and the capacity retention rate decreases under the same test conditions.

[0115] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Therefore, any simple modification, equivalent change and modification of the above embodiment according to the technical essence of the present application, without departing from the technical scheme of the present application, shall fall within the protection scope of the technical scheme of the present application.

Claims

1. A titanium-doped high-nickel ternary cathode material, characterized in that, The titanium-doped high-nickel ternary cathode material comprises a high-nickel ternary cathode material and a titanium-doped element; the high-nickel ternary cathode material has a chemical formula of LiNi x Co y Mn (1-x-y) O2, wherein 0.75 < x < 0.95 and 0.025 < y < 0.1; the titanium-doped element is derived from a titanium-containing compound with reducibility, mixed and sintered with the high-nickel ternary cathode material to form the doping, the sintering is to heat to 300-500℃ at a heating rate of 1-10℃ / min for 3-5h, the sintering allows the titanium-containing compound with reducibility to be adsorbed on the surface of the high-nickel ternary material, and Ti 2+ reacts with Ni 3+ to make Ti 4+ better enter the material lattice to form a stable Ni 2+ layer; the content of the titanium-doped element is 0.5-5wt% of the titanium-doped high-nickel ternary cathode material, and the titanium-containing compound with reducibility includes one or more of titanium monoxide, titanium dichloride and titanium dibromide.

2. The titanium-doped high-nickel ternary cathode material of claim 1, characterized in that, The high-nickel ternary positive electrode material is a spherical secondary particle agglomerate with a particle size of 2-4 μm.

3. The method for preparing the titanium-doped high-nickel ternary cathode material according to claim 1 or 2, characterized in that, The method comprises the following steps: (1) preparing a nickel-cobalt-manganese hydroxide precursor by a coprecipitation reaction; (2) mixing the nickel-cobalt-manganese hydroxide precursor obtained in step (1) with a lithium source uniformly, and then performing two-stage sintering in an oxidizing atmosphere, and cooling to room temperature to obtain the high-nickel ternary positive electrode material; (3) mixing the high-nickel ternary positive electrode material obtained in step (2) with a reducing titanium source uniformly; (4) sintering the mixed powder obtained in step (3) at high temperature in an inert atmosphere, and cooling to obtain the titanium-doped high-nickel ternary positive electrode material.

4. The preparation method according to claim 3, characterized in that, In step (1), the preparation of the nickel-cobalt-manganese hydroxide precursor by the coprecipitation reaction refers to pumping a nickel-cobalt-manganese mixed solution into a continuous stirring reaction kettle provided with an ammonia solution, heating, and introducing a protective atmosphere, while pumping a complexing agent and a precipitant solution, stirring to perform the coprecipitation reaction, aging, filtering, washing, and drying to obtain the nickel-cobalt-manganese hydroxide precursor.

5. The preparation method according to claim 4, characterized in that, The nickel source, the manganese source, and the cobalt source in the nickel-cobalt-manganese mixed solution are respectively a soluble nickel salt, a soluble manganese salt, and a soluble cobalt salt; the total molar concentration of nickel ions, cobalt ions, and manganese ions in the nickel-cobalt-manganese mixed solution is 0.1-3.0 mol / L, and the molar ratio of nickel ions, cobalt ions, and manganese ions is (7.5-9.5):(0.25-2.5):(0.25-2.5). The feeding speed of the nickel-cobalt-manganese mixed solution is 80-120 mL / h.

6. The preparation method according to claim 4, characterized in that, The complexing agent is an ammonia solution, and the mass concentration of the ammonia in the ammonia solution is 25-28%; the ammonia concentration in the reaction system is adjusted to 0.1-5.0 mol / L by using the ammonia solution. The precipitant is one or more of sodium hydroxide, potassium hydroxide, or lithium hydroxide, and the molar concentration of the precipitant solution is 1.0-7.0 mol / L; the pH value of the reaction system is adjusted to 10-12 by using the precipitant solution. The volume ratio of the ammonia solution, the precipitant solution, and the nickel-cobalt-manganese mixed solution is (0.1-10):(1-2):(1-2).

7. The preparation method according to claim 4, characterized in that, The stirring speed during the coprecipitation reaction is controlled to be 800-1200 r / min, the temperature is 30-60℃, and the time is 30-50 h. The aging temperature is 30-60℃. The washing is cross washing of the filter with deionized water and ethanol for not less than 6 times. The drying temperature is 80-100℃, and the time is 12-24 h.

8. The preparation method according to claim 3, characterized in that, In step (2), the two-stage sintering is first heated to 350-550℃ at a heating rate of 1-10℃ / min, sintered for 2-8 h, and then heated to 550-1000℃ at a heating rate of 1-10℃ / min, sintered for 8-20 h.

9. The production method according to any one of claims 3 to 8, characterized by, In step (3), the mass ratio of the high-nickel ternary positive electrode material to the reducing titanium source is 1:(0.005-0.05); the titanium source is one or more of titanium monoxide, titanium dichloride, and titanium dibromide.

10. The method of claim 9, wherein, In step (4), the high-temperature sintering is heating to 300-500℃ at a heating rate of 1-10℃ / min, and sintering for 3-5 h; the inert atmosphere is an argon atmosphere and / or a nitrogen atmosphere.

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